This invention is directed to novel chemical compounds and to their use as herbicides and plant growth regulants. Specifically, this invention relates to phosphonium salts of N-phosphonomethylglycine.
N-Phosphonomethylglycine is a well-known chemical agent, sold commercially as the mono-isopropylamine salt for herbicide applications and as the sodium salt for the growth regulation of sugar cane. The manufacturer of the salts is Monsanto Agricultural Products Company, St. Louis, Mo. Various other salts are known, including substituted ammonium salts, alkali metal salts, and alkaline earth metal salts.
A new class of salts of N-phosphonomethylglycine has now been discovered to be effective as postemergence herbicides and plant growth regulants. Whether a herbicidal or growth regulant effect will be achieved depends on the crop to which the salts are applied, the method of application, the type and extent of weeds present, and the application rate. Determination of the proper combination of such factors is well within the routine skill of those skilled in the art of agriculture.
Herbicidal effects range from partial control to complete kill of weeds or generally undesired vegetation. Partial rather than complete control is sometimes preferred for purposes of economics or minimization of accompanying crop injury (depending on the crop to be protected). Plant growth regulant effects are somewhat more varied and include defoliation and retardation of vegetative growth.
Defoliation can be used to enhance the growth of productive plant parts and to facilitate harvesting. This is particularly useful in flax, cotton, and bean crops. Although defoliation kills leaves, it does not harm the rest of the plant and is thus not a herbicidal action. In fact, killing the plant itself is detrimental to defoliation since leaves adhere more strongly to a dead plant.
The retardation of vegetative growth is useful in a variety of ways. In certain plants it causes a diminution or elimination of the normal apical dominance, leading to a shorter main stem and increased lateral branching. Smaller, bushier plants with increased resistance to drought and pest infestation are the result. Retardation of vegetative growth is also useful in turf grasses for lessening the vertical growth rate, enhancing root development, and producing a denser, sturdier turf. The retardation of turf grasses also serves to increase the interval between mowings of lawns, golf courses and similar grassy areas. In silage crops, potatoes, sugar cane, beets, grapes, melons and fruit trees, the retardation of vegetative growth increases the carbohydrate content of the plants at harvest. It is believed that growth retardation or suppression at the appropriate stage of development decreases the amount of carbohydrate available for vegetative growth and thereby enhances starch and/or sucrose content. Retardation of vegetative growth in fruit trees produces shorter branches and greater fullness of shape, and often results in lesser vertical elongation. These factors contribute to the ease of access to the orchard and simplify the fruit harvesting procedure.